Polycarbonate resins are generally produced using bisphenols or the like as monomer ingredients, and are in extensive use as so-called engineering plastics in the fields of electrical/electronic parts, automotive parts, medical parts, building materials, films, sheets, bottles, optical recording media, lenses, etc. so as to take advantage of the superiority thereof concerning transparency, heat resistance, mechanical strength, etc.
Recently, polycarbonate resins induced from a dihydroxy compound having a fluorene ring as a side chain have been reported.
Patent document 1 describes a polycarbonate resin having excellent optical properties which has been produced using a bisphenol compound having a fluorene ring as a side chain and 2,2-bis(4-hydroxyphenyl)propane. Patent document 2 describes a polycarbonate resin which has a low photoelastic coefficient and has been produced using a bisphenol compound having a fluorene ring as a side chain, pentacyclodecanedimethanol, and isosorbide. Patent document 3 describes a polycarbonate resin produced using a dihydroxy compound having a fluorene ring as a side chain, tricyclodecanedimethanol, and isosorbide. Furthermore, patent document 4 discloses that a retardation film made of such a polycarbonate resin which contains fluorene rings not only has a low photoelastic coefficient but also shows reverse wavelength dispersion characteristics, i.e., the property of decreasing in phase retardation as the wavelength decreases, and that a polycarbonate which is useful in optical applications including retardation films is hence obtained.
In the case where a polycarbonate resin is to be produced using a dihydroxy compound having alcoholic hydroxyl groups, such as the dihydroxy compound having a fluorene ring as a side chain or isosorbide, or the like as a starting material, the resin usually is produced by a method called a transesterification process or a melt process. According to this method, polycarbonate resins have been obtained by subjecting the dihydroxy compound to transesterification with a carbonic diester, e.g., diphenyl carbonate, at a high temperature in the presence of a basic catalyst and removing the resultant by-product phenol from the system to thereby cause the polymerization to proceed.
In recent years, the technique of film formation by melt extrusion, in which films are formed without using a solvent, has come to be employed in order to more efficiently produce molded articles which are thin and have a large area, such as films. Resins for use in this technique are required to have melt processability, and various copolymer compositions have been proposed from this standpoint (see, for example, patent document 5 to patent document 8).